At meeting in Washington, D.C., last month, conservationists and ape experts learned that Ebola has taken hold in Odzala National Park in the Republic of the Congo.

"Odzala is being hammered," said Peter Walsh, an ecologist at the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany. "Before the arrival of Ebola, this park held the single largest population of gorillas and chimpanzees in the world."

The warning follows a year-long survey in the region by the Programme for Conservation and Rational Utilization of Forest Ecosystems in Central Africa (ECOFAC), a conservation initiative sponsored by the European Union.

Ape experts said they fear that Ebola could infect all remaining large populations of great apes in western equatorial Africa within the next five years. The region encompasses Cameroon, Congo, Gabon, Equatorial Guinea, and the Central African Republic.

"Immediate action is required to determine how best to ensure this doesn't happen," said Diane Doran, a gorilla researcher at Stony Brook University on Long Island, New York.

Conservationists said urgent action may stop the virus from spreading. Steps include:

 patrolling riverbanks to cut downed trees, which apes use as natural bridges, and  pressing ahead with experimental Ebola vaccines to inoculate wild great ape populations within three to five years.

Some experts say intervening to stop the spread of Ebola in great apes may also help protect human populations in the region. Most recent outbreaks of the virus in humans have been traced back to the handling of infected ape carcasses.

Ebola River

The Ebola virus is named after the Ebola River, site of the first known outbreak of the disease in 1976. The highly contagious virus causes fever and hemorrhaging that often proves fatal.